Many species of fish are farmed offshore in large net pens. One of the most popular is salmon. There is a major problem today with infestation of sea lice on farmed salmon. With the salmon industry growing rapidly, the close proximity and cross contamination makes managing sea lice on salmon challenging.
Sea lice are marine copepods of the family Caligidae, with several each of the species Lepeophtherius and Caligus species. They are a naturally occurring parasite that have existed on wild fish well before salmon farming efforts, although there is speculation that farming efforts have increased the spread of lice to wild fish. Populations of sea lice on fish are no threat to humans, but they leave marks on fish that lower market value and increase likelihood of disease. Currently, environmentalist claim that sea lice cause mortalities on salmon fingerlings returning to the ocean from rivers and, therefore, fewer fingerling survivors and fewer mature adult spawning river returns.
Treatment for sea lice infestations can take many forms in a farm environment. Several chemical treatments are currently available, the most prevalent being SLICE (Emamectin benzoate EMB). SLICE can be presented to fish through inclusion in feed. Each application technique has obvious drawbacks. Application techniques are difficult to control effective dosage, and neither have a mechanism to prevent the SLICE from entering into the environment.
Other treatments involve bathing salmon in a solution of hydrogen peroxide. It is not harmful to the environment, so it can be pumped back into the ocean. Removing high percentages of lice with hydrogen peroxide is very expensive due to the high capital cost in the form of specialized equipment. Crowding and conventional pumping can cause undue stress on the fish, leading to temporary reduced feeding and growth, degrading marks and or mortalities. Bathing fish in fresh and warm water can also be effective, but at a huge cost of energy and handling. Salmon farmers and government regulators are responding, creating huge cost increases to control the problem.